Inherits: If T is a (possibly cv-qualified)
class type then inherits from true_type,
otherwise inherits from false_type.

C++ Standard Reference: 3.9.2 and 9.2.

Header:#include<boost/type_traits/is_class.hpp>
or #include<boost/type_traits.hpp>

Compiler Compatibility: Without (some as
yet unspecified) help from the compiler, we cannot distinguish between union
and class types, as a result this type will erroneously inherit from true_type for
union types. See also is_union.
Currently (May 2005) only Visual C++ 8 has the necessary compiler intrinsics
to correctly identify union types, and therefore make is_class function correctly.